Field of the Invention
The present invention relates to an object information acquiring apparatus and a method of controlling the apparatus.
Description of the Related Art
Photoacoustic imaging is a method of visualizing the three-dimensional structure of the inside of an object by irradiating the object with light such as laser pulses and detecting photoacoustic waves that are generated by thermal expansion. With the use of light of various wavelengths, a distribution of a substance that absorbs a particular wavelength, such as hemoglobin or glucose in blood, can be visualized. As the method enables non-invasive detection of neovascular vessels that are characteristic of a tumor, it is attracting attention as means of early detection of breast cancer.
A specific procedure of a conventional photoacoustic imaging method is disclosed in Japanese Translation of PCT Application No. 2001-507952, for example, as follows:
(Step 1) A probe with two-dimensional arrays of receiving elements (2D probe) that convert an acoustic wave into an electrical signal is placed on the surface of an object, and the object is irradiated with single pulsed electromagnetic energy.
(Step 2) Signals received by each receiving element are sampled and stored, from immediately after the irradiation with electromagnetic energy.
(Step 3) A delay time for an acoustic wave to propagate from a point of interest in the object to the position of each receiving element is calculated, and the delay time is added to the corresponding received signal to obtain the intensity of the image data of the point of interest.
(Step 4) Step 3 is repeated for each point of interest to be visualized.
Japanese Patent Application Laid-open No. 2005-21380 discloses a method of reconstructing an image from both of a photoacoustic image and a normal ultrasound image using a common probe with a one-dimensional array of receiving elements (1D probe). To reconstruct a three-dimensional image of a wide area with this 1D probe, the probe needs to be moved mechanically in a direction orthogonal to the direction in which the receiving elements are arranged.    Patent Literature 1: Japanese Translation of PCT Application No. 2001-507952    Patent Literature 2: Japanese Patent Application Laid-open No. 2005-21380